13 research outputs found
Lifetimes of the b-flavored baryons in the light-front quark model
The calculation of lifetimes of heavy-flavored baryons in the light-front
quark model approach is briefly reviewed.Comment: 4 pages, proceedings of the IV International Conference on Hyperons,
Charm and Beauty Hadrons, Valencia, June 27--30, 200
Electromagnetic form factors of the meson in a light-front constituent quark model
The electromagnetic form factors of the meson are evaluated adopting a
relativistic constituent quark model based on the light-front formalism, and
using a meson wave function with the high-momentum tail generated by the
one-gluon-exchange interaction. The breakdown of the rotational covariance for
the one-body component of the current operator is investigated and the
sensitivity of the ratio of the -meson form factors to the pion (charge)
form factor to the spin-dependent component of the effective
interaction is illustrated.Comment: 8 pages, latex file, 4 figures available as a separate .uu fil
Charmed decays of the B-meson in the quark model
Exclusive and inclusive, semileptonic and non-leptonic, charmed decays of the
B-meson are investigated in the context of a phenomenological quark model.
Bound-state effects are taken care of by adopting a single (model-dependent)
non-perturbative wave function, describing the motion of the light spectator
quark in the B-meson. A nice reproduction of both exclusive and inclusive
semileptonic data is obtained. Our predictions for the electron spectrum are
presented and compared with those of the Isgur-Scora-Grinstein-Wise quark
model. Finally, our approach is applied to the calculation of inclusive
non-leptonic widths, obtaining a remarkable agreement with experimental
findings.Comment: to appear in the Proc. of the 2^{nd} Int. Conf. on Hyperons, Charm
and Beauty Hadrons, Montreal, Canada, 27-30 August 199
The general relation between the weak inclusive decays of bound and free heavy quarks
We derive a new parton formula for the inclusive B decays and briefly discuss
its applications to semileptonic and weak radiative decays of the B-meson.Comment: espcrc2.sty (included), 3 pages, Presented at the Third International
Conference on Hyperons, Charm and Beauty Hadrons, Genova, June 30 --July 3,
1998, to appear in proceeding
The non-perturbative corrections to the photon spectrum in a parton-like model
We derive a new parton-like formula, which establishes a simple connection
between the electroweak decay rate ) and the rate
of a free b-quark decay. The main features of our approach are the treatment of
the b-quark as an on-mass-shell particle and the inclusion of the effects
arising from the b-quark transverse motion in the -meson. Using various
b-quark light-front (LF) distribution functions, both phenomenological one and
the ones derived from current constituent quark models, and neglecting
perturbative corrections we compute the photon energy spectra and the moments
of the shape function. It is shown that the parton-like approach is fully
consistent with the Heavy Quark Effective Theory (HQET) provided the b-quark
constituent mass is redefined in the way similar to that used in HQET to define
the pole mass of the b quark. In this way the correction to first order in
can be eliminated from the total width in agreement with the general
statement of HQET. We have also found that the photon energy spectra calculated
in the LF approach agree well with the ones obtained in the ACM model, provided
the same distribution function is used as input in both cases. In spite of the
simplicity of the model our results show a fair good agreement both with the
HQET predictions and available experimental data.Comment: 14 pages, LaTeX, 3 ps figure
The Kalman-Tran-D'Souza Model and the Semileptonic Decay Rates of Heavy Baryons
We present an investigation of the inclusive semileptonic decay widths of the
heavy baryons Lambda_Q and Xi_Q, (Q=b,c) performed within a relativistic
constituent quark model, formulated on the light-front. In a way conceptually
similar to the deep-inelastic scattering case, the H_Q baryon inclusive width
is expressed as the integral of the free Q-quark partial width multiplied by a
bound-state factor related to the Q-quark distribution function in the H_Q. The
non-perturbative meson structure is described through the quark-model wave
functions, constructed via the Hamiltonian light-front formalism using as input
the Kalman-Tran-D'Souza equal time wave functions. A link between spectroscopic
quark models and the H_Q decay physics is obtained in this way. It is shown
that the bound-state effects and the Fermi motion of the b-quark remarkably
reduce the decay rate with respect to the free-quark result. Our predictions
for the BR(Lambda_c ->X_s e nu_e) and BR(Lambda_b->X_c e nu_e) decays are in
good agreement with existing data.Comment: 6 pages, latex, espcrc2.sty (included), 3 figures. The invited talk
presented by C.S.K. at the 4-th International Conference on Hyperons, Charm
and Beauty Hadrons, Valencia, June 27-30, 200
Radiative and transition form factors in a light-front constituent quark model
The form factors of the and radiative transitions are
evaluated within a light-front constituent quark model, using for the first
time the eigenfunctions of a light-front mass operator reproducing the meson
mass spectrum and including phenomenological Dirac and Pauli quark form factors
in the one-body electromagnetic current operator. The sensitivity of the
transition form factors both to the meson wave functions and to the constituent
quark form factors is illustrated. It is shown that the measurement of the and radiative transitions could help in discriminating among
various models of the meson structure.Comment: 9 pages, latex, 4 figures available as separate .uu file, to appear
in Phys. Lett.
Hard Constituent Quarks and Electroweak Properties of Pseudoscalar Mesons
The high momentum components generated in the wave function of pseudoscalar
mes* by the one-gluon-exchange interaction are investigated within a
relativistic constituent quark model. Adopting the light-cone formalism, the
sensitivity of the weak decay constant and the charge form factor to hard
constituent quarks is illustrated.Comment: 11 pages and 5 figs. (to be requested), LaTeX, INFN-ISS 94/3. To
appear in Physics Lett.
A connection between inclusive semileptonic decays of bound and free heavy quarks
A relativistic constituent quark model, formulated on the light-front, is
used to derive a new parton approximation for the inclusive semileptonic decay
width of the B-meson. A simple connection between the decay rate of a free
heavy-quark and the one of a heavy-quark bound in a meson or in a baryon is
established. The main features of the new approach are the treatment of the
b-quark as an on-mass-shell particle and the inclusion of the effects arising
from the b-quark transverse motion in the B-meson. In a way conceptually
similar to the deep-inelastic scattering case, the B-meson inclusive width is
expressed as the integral of the free b-quark partial width multiplied by a
bound-state factor related to the b-quark distribution function in the B-meson.
The non-perturbative meson structure is described through various quark-model
wave functions, constructed via the Hamiltonian light-front formalism using as
input both relativized and non-relativistic potential models. A link between
spectroscopic quark models and the B-meson decay physics is obtained in this
way. Our predictions for the B -> X_c l nu_l and B -> X_u l nu_l decays are
used to extract the CKM parameters |V_cb| and |V_ub| from available inclusive
data. After averaging over the various quark models adopted and including
leading-order perturbative QCD corrections, we obtain |V_cb| = (43.0 +/-
0.7_exp +/- 1.8_th) 10^-3 and |V_ub| = (3.83 +/- 0.48_exp +/- 0.14_th) 10^-3,
implying |V_ub / V_cb| = 0.089 +/- 0.011_exp +/- 0.005_th, in nice agreement
with existing predictions.Comment: revised version with pQCD corrections included, to appear in Physical
Review